# -*- coding: utf-8 -*-
#
import numpy


def _z():
    return numpy.array([[0.0, 0.0]])


def _s8(a, b):
    return numpy.array([
        [+a, +b],
        [-a, +b],
        [+a, -b],
        [-a, -b],
        [+b, +a],
        [-b, +a],
        [+b, -a],
        [-b, -a],
        ])


def _s4(a):
    return numpy.array([
        [+a, +a],
        [-a, +a],
        [+a, -a],
        [-a, -a],
        ])


def _s40(a):
    return numpy.array([
        [+a, 0.0],
        [-a, 0.0],
        [0.0, +a],
        [0.0, -a],
        ])
